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ANOTHER WARMEST ‘SAME WEEK’ IN DECADES / JASON UPDATE

By: Steve Gregory , 09:03 PM GMT am 14. Februar 2017


TUESDAY: 14-FEB-17 / 3:00 PM CST

UNUSUAL WARMTH & STRONG STORM SYSTEMS AHEAD
INCREASING CHANCES FOR COLDER WX IN EARLY MARCH

The highly progressive flow that has prevailed this winter - in combination with an especially strong large-scale mean TROF over the EPAC - will continue to bring strong short wave TROFS /storm systems into the southwestern US every few days while simultaneously building a strong ridge over the central and then eastern US. This general pattern is expected to persist through the end of the month before a possible pattern shift evolves in early MAR.

After each strong short wave TROF /storm system comes onshore (with the potential for more flash flood and mud slide risks in CA), they are expected to move eastward towards the Gulf coast states – staying south of the upper level ridge expected to be in place over the center of the nation. While it is too early to say with any certainty that severe T-storms / tornadoes will occur – the expected pattern appears likely to support 2 or more severe WX outbreaks across the Gulf coast states during the remainder of the month.

A major driving force of the current pattern is a strong MJO now moving towards the central equatorial Pacific and has been destructively interfering with the low frequency atmospheric base state that has prevailed this winter. As the MJO moves into Phase 1 & 2, associated tropical forcing onto the mid-latitude flow pattern across the Pacific will weaken, with model trends now suggesting the development of a ridge in the west and a TROF (and more seasonal Temps) in the east by early MAR.

ENSO TRANSITION IN PROGRESS

Officially, La Niña has ended as SST anomalies within the ENSO region are back near normal. However, other atmospheric indicators continue to be characteristic of La Nina. That said, with the passage of the strong MJO across the Pacific (the strongest since last spring), a significant oceanic Kelvin Wave has been triggered. The KW is already leading to warming of SST’s in the WPAC - and this warming is forecast to advance into the EPAC over the next month. With this development – along supporting climate model forecasts - the development of El Niño conditions later this year is becoming a distinct possibility.




Fig 1: PAST 30 & 90 TEMP ANOMALIES Temp anomalies during the past 30 days have averaged 8˚F or more above normal east of the Rockies, with only the PAC NW remaining below normal. This is similar to the 90-Day Temp anomaly pattern, with Temps averaging 3˚-5˚F above normal since mid NOV – rather amazing since this period includes nearly 4 weeks of well below normal Temps in the eastern half of the nation.



CLICK (TOP) IMAGE To Open FULL Size image in a new window

Fig 2: TELECONNECTION FORECASTS (GFS ENSEMBLE) A warmer than normal Temp pattern is supported by all 3 Teleconnections as the AO and NAO move into a positive phase while the PNA shifts back towards neutral. (Some models, not shown, actually suggest a negative PNA phase will develop by next week – and this is very supportive of warmer than normal conditions thru the end of the month.)


Fig 3: GLOBAL MODEL FORECASTS FOR THE MJO After nearly 6 months of very weak MJO cycles – we have a very robust MJO moving thru Phase 8 and will eventually move into Phase 1 / 2 as it weakens during Week 2. Longer range, ECMWF based forecast products suggest another significant MJO will develop in the Indian Ocean during March.


Fig 4: OUTGOING LONG-WAVE RADIATION (OLR) Even though SST’s have now returned to near normal in the tropical EPAC, several atmospheric metrics, including the above satellite derived OLR showing below normal cloudiness near the Dateline - remain indicative of a La Niña base state. However, with the MJO now moving towards the central Pacific, above normal cloudiness and convection is likely to develop in the central and then eastern Pacific during the week ahead.


Fig 5: UPPER OCEAN HEAT ANOMALIES ACROSS EQUATORIAL PACIFIC The below normal oceanic heat content in the equatorial Pacific that developed last summer is now rapidly weakening, with significant warming over the WPAC. It also appears that the MJO has triggered a significant Kelvin Wave in the WPAC; and this KW is seen propagating across the Pacific during the spring. This in turn should lead to warming SST’s – raising the prospect for the development of an El Niño condition during the summer or fall season - especially if we see additional, strong MJO’s and potential Westerly Wind Bursts (WWB).


Fig 6: CFSv2 ENSO FORECAST The latest CFS forecast for a sharp rise in SST anomalies within the ENSO 3.4 Region during the next 4 weeks – and this is a reasonable expectation as a result of the current MJO cycle strength. There is considerable uncertainty in the longer ranges – and this is typical of model forecasts during the spring season. Still, the prospect for an El Nino going into next winter is a real one.



Fig 7a/b: Operational GFS 500mb (≈ 18,000 Ft) Height Forecast Loop for the next 2 Weeks (Top) and corresponding 250mb ( ≈35,000 Ft) Wind Forecast Loop (Bottom) The highly progressive flow continues thru the period with the mean, synoptic scale TROF in the EPAC seen retrograding towards the west by the end of the month while a ridge begins to develop in the west. Until then, however, frequent storm/frontal systems are expected to move into the SW US and then heading towards the Gulf coast region … The very strong east-west orientated polar jet stream over the Pacific will continue to send strong short wave / storm systems into the SW US, with periodic intensification of the sub-tropical jet stream ahead of each system as they move onshore. This may result in torrential rainfall events over California during the next 10 days. As the systems reach the Gulf states region, the strong jet streams combined with increased surface (and moisture) convergence will raise the prospect of severe T-storm and tornadic activity.


Fig 8: CFSv2- TEMP ANOMALY FORECAST The latest CFS (Climate Model) forecast for MARCH suggests the general anomaly pattern observed this winter will continue during MAR and is supported by OPNL and Ensemble model trends. While the CFS model does not have a ‘stellar’ record, it has shown some skill over the past 3 years relative to pure chance. This forecast is also supported by the NMME ensemble climate model (not shown).


Fig 9: 2016 High Temporal Resolution Surface Height (SSH) Anomalies from the JASON (NASA) Satellite platform highlighting since AUG 1, 2016: The above looped imagery is assembled EVERY day (the highest temporal resolution available), showing the evolution out of last years’ El Niño into the ‘weak’ La Nina that is now gone. (As discussed elsewhere, SST’s alone do NOT fully characterize an ENSO event.) Warmer water occupies a greater volume than cold water, so higher than normal Sea Surface Heights (SSH) depicted by the warmer color tones correlate with warmer than normal ocean Temps – while colder ocean waters correlate with lower than normal SSH’s. Keep in mind that actual SST anomalies do NOT always correspond on a one-to-one basis with Total Ocean Heat Content (OHC) of the corresponding column of water , which is generally represented by the JASON SSH anomalies. As La Niña developed during the Fall, SSH’s in the ENSO region fell off to slightly below normal levels even as above normal readings persisted to the north of the ENSO region proper, while a strip of cooler waters can be seen further north. The warmer waters likely contributed to the development of especially strong Precip events in CA. Of note, is the effective demise of sub-surface warmth in the Gulf of Alaska (GOA) region which some believe had led to the ‘ridiculously resilient ridge’ in the West during the 2012-2015 winter seasons.


Fig 10: Temperature ANOMALY forecast for Week 1 is based STRICTLY on the MOS data forecasts from today’s 12Z operational GFS model run (with only minor adjustments towards the raw model data points for Days 6-8). Warmer than normal Temp anomalies will dominate the nation during Week 1 – with extremely warm anomalies over the central US. The only real exception will be in CA where at least 2 distinct storm systems will keep daytime Temps near normal. Overall confidence is very high with excellent temporal and regional model agreement – with a reading of ‘5’ for the pattern and ‘4’ for actual anomaly magnitudes on a scale of 1 to 5.



Fig 11: The Week 2 Temperature ANOMALY forecast is based on the 12Z run of the GFS (80%) integrated with the 12Z GFS Ensemble (5%), ECMWF Ensemble (5%) and Climatology (10%) using the projected pattern along with explicit surface and 850mb (~5,000 FT) Temp forecasts. Some Temps are adjusted for known or expected anomalous thermal patterns & projected storm system passages.ON AVERAGE, warmer than normal Temp anomalies should persist east of the Rockies during Week 2. However, daily anomalies will be declining during the second half of the week. Overall confidence is near average for the anomaly pattern but a bit below normal for this time of year due significant differences between model runs for Days 11-16 with a reading of ‘3’ for the pattern but only ‘2’ for actual anomaly magnitudes on a scale of 1 to 5.

Steve


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

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13. WunderAlertBot (Admin)
07:54 PM GMT am 21. Februar 2017
SteveGregory has created a new entry.
12. Snacker2
07:43 PM GMT am 21. Februar 2017
Quoting 11. georgevandenberghe:



That underwhelming sound of my jaw not dropping :-)

My soil is workable, moist but not wet and friable here in Maryland the last week in February. I have a few daffodils. I've put away the garden covers (needed when temps go below 20F). I may have to get them back out but my hunch is not. I have half of my 2.5 cords of firewood left. I've planted broccoli seedlings outside and peas will go in next weekend. I went to the rental garden and got a huge haul of surviving broccoli, spinach and brussels sprouts.

Our warmest feb of 1976 still looks safe. Warmest winter 1932 also looks safe. We've had other winters this mild, 2001-2 and 2011-12 come to mind


This week of April in February has tulips and daffodils popping out in WI. They will die. Far too early.
Member Since: Dezember 31, 1969 Posts: Comments:
11. georgevandenberghe
03:30 PM GMT am 21. Februar 2017
Quoting 10. SteveGregory:



Overall, the ECMWF did better in the extended outlook.

Steve


That underwhelming sound of my jaw not dropping :-)

My soil is workable, moist but not wet and friable here in Maryland the last week in February. I have a few daffodils. I've put away the garden covers (needed when temps go below 20F). I may have to get them back out but my hunch is not. I have half of my 2.5 cords of firewood left. I've planted broccoli seedlings outside and peas will go in next weekend. I went to the rental garden and got a huge haul of surviving broccoli, spinach and brussels sprouts.

Our warmest feb of 1976 still looks safe. Warmest winter 1932 also looks safe. We've had other winters this mild, 2001-2 and 2011-12 come to mind
Member Since: Dezember 31, 1969 Posts: Comments:
10. Steve Gregory , Sr. Forecaster/Risk Analysis
09:30 PM GMT am 20. Februar 2017
Quoting 8. WU-547442:

Hi Steve,

I remembered you mentioning that the GFS and European models diverged substantially for early/late February predictions. In hindsight, which one came closer?

Thanks


Overall, the ECMWF did better in the extended outlook.

Steve
Member Since: Dezember 31, 1969 Posts: Comments:
9. WU-501842
07:14 PM GMT am 20. Februar 2017
Steve,

I’m curious about how this most recent Arctic Stratospheric Event (ASE) might foreshadow our spring. Forgive me my awkward phrasing as in Meteorology, trained I was not. I understand that my linking data points doesn’t reveal a grasp of the weather in this case, so allow me my thought experiment.

Last late winter early spring there was a very strong Arctic Stratospheric Event (ASE). In the northeast US, we had a damp and chilly April and May. Adding this to a research paper on how disruption of the Arctic low caused the NE to have cool damp springs. I hope someone remembers this piece, possibly by a researcher at Harvard, and can add it to this conversation.

Here is the grand prize question, how likely is the most recent ASE to bias the Northeast toward a cool April? I’d appreciate the sharing of your wisdom, experience and thinking process on how this might play out. In June we will know how the weather developed, but where is the fun in just waiting?

Oldie,
When in predicament that you see no way out, ask an old timer. They’ve been there themselves or seen another work free.
Member Since: Dezember 31, 1969 Posts: Comments:
8. WU-547442
03:08 PM GMT am 20. Februar 2017
Hi Steve,

I remembered you mentioning that the GFS and European models diverged substantially for early/late February predictions. In hindsight, which one came closer?

Thanks
Member Since: Dezember 31, 1969 Posts: Comments:
7. Steve Gregory , Sr. Forecaster/Risk Analysis
08:44 PM GMT am 16. Februar 2017
Quoting 6. WU-614742:

I think if its possible to add an "s" to the image links "https://" then the images should show up on the Browsers that have issues seeing the images. The main URL address of the blog is https so i think when an image in the page is not also "s" then it doesn't show for security reasons/rules settings.
Some browsers are more strict than others: I can see the images in my current version of Chrome but not my current version of firefox.



If I post using https: the images don't show up in IE 11. Very weird issues...

Steve
Member Since: Dezember 31, 1969 Posts: Comments:
6. WU-614742
06:00 PM GMT am 16. Februar 2017
I think if its possible to add an "s" to the image links "https://" then the images should show up on the Browsers that have issues seeing the images. The main URL address of the blog is https so i think when an image in the page is not also "s" then it doesn't show for security reasons/rules settings.
Some browsers are more strict than others: I can see the images in my current version of Chrome but not my current version of firefox.
Member Since: Dezember 31, 1969 Posts: Comments:
5. RFinNHWx
12:08 PM GMT am 15. Februar 2017
Pale Moon is a 64 bit mozilla browser and images load fine- Excellent browser-

Chrome is an invalid browser and is used sparingly... I removed the following switches on tic boxes in adv settings and then ran browser "incognito", and images appear normal, and lessthan browser remains stable-

Just the switches change, resulted in browser displaying mages, then locking up- [like the useless techballon that crossed the moon, the other eve during eclipse]

Try "incognito" in chrome, as well as removing switches in advanced settings named:
[Use a web service...]
[use a prediction service...]
[use a prediction service...]

Or try Pale Moon

IE any version should be disabled permanently, and the corporation responsible should do time in a box; just like a person!
Member Since: Dezember 31, 1969 Posts: Comments:
4. Alan8156
11:41 AM GMT am 15. Februar 2017
Thanks, Steve.

I'm viewing this on a six-year old Apple laptop with an outdated version of Chrome, and the graphics display fine. Weird.
Member Since: Dezember 31, 1969 Posts: Comments:
3. Some1Has2BtheRookie
11:47 PM GMT am 14. Februar 2017
Quoting 2. HotToddy62:

Steve,
Still very strange. I mostly use Chrome Version 56.0.2924.87 for the web, but your pictures do not show up (still). The pictures show up fine on Dr. Masters blog and Ricky Rood's blog, but not yours. Your pictures show up fine in Internet Explorer 11. Again, strange.
PS going to be extremely nice for the end of February in Des Moines


I have the same problem with the images. I can right click on the image placeholder and "View Image" and the image will display.

California needs a bit more rain, just not too much at one time.
Member Since: Dezember 31, 1969 Posts: Comments:
2. HotToddy62
10:20 PM GMT am 14. Februar 2017
Steve,
Still very strange. I mostly use Chrome Version 56.0.2924.87 for the web, but your pictures do not show up (still). The pictures show up fine on Dr. Masters blog and Ricky Rood's blog, but not yours. Your pictures show up fine in Internet Explorer 11. Again, strange.
PS going to be extremely nice for the end of February in Des Moines
Member Since: Dezember 31, 1969 Posts: Comments:
1. Snacker2
09:48 PM GMT am 14. Februar 2017
Oh those temp maps look GORGEOUS. Spring in February. Woo! BBQ has to be thrown.
Member Since: Dezember 31, 1969 Posts: Comments:

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About SteveGregory

Professional Forecaster experience since 1977, concentrating in Aviation, Tropical and Long Range forecasting.

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